He co-founded Cygnus Solutions in 1989. His programming contributions to free software include authorship of the GNU C++ compiler and work on the GNU C compiler and the GNU Debugger. Tiemann is featured in the 2001 documentary Revolution OS. Opensource.com profiled him in 2014, calling him one of "open source's great explainers."
He was the chief technical officer of Red Hat. He served on a number of boards, including the Embedded Linux Consortium, the GNOME Foundation advisory board, and the board of directors of ActiveState Tool Corp.
- "Michael Tiemann, V.P. of Red Hat Open Source Affairs, Selected as City of Raleigh 2015 Environmental Awards Keynote" (Press release). City of Raleigh. December 26, 2014.
- Tiemann, Michael. "Home page for Michael Tiemann". Archived from the original on 2002-01-03. Retrieved 2015-02-21.
- Thank You Michael Tiemann!
- Interview with Red Hat Vice President, Open Source Affairs - Michael Tiemann
- FORTUNE VISITS 25 COOL COMPANIES: What has the computer revolution done for us lately?
- Future of Cygnus Solutions: An Entrepreneur's Account, by Michael Tiemann (1999)
- Stallman, Richard M. (February 1988). "GNUs Flashes, February 1988". GNU's Bulletin.
- "About". Revolution OS.
- Behrenshausen, Bryan (August 5, 2014). "How to think like open source pioneer Michael Tiemann". Opensource.com. Opensource.com. Retrieved December 19, 2015.
- "Red Hat Executive Team". Red Hat. Archived from the original on 2003-10-03.
- "Red Hat CTO Michael Tiemann Appointed to Embedded Linux Consortium Board of Directors" (Press release). Red Hat. June 21, 2000.
- Veillard, Daniel (2003-03-13). "Minutes of the GNOME Board meeting March 11 2003". foundation-announce (Mailing list). Retrieved 2015-02-21.
- "NY VC funds ActiveState" (Press release). ActiveState. 2000-09-25.
ActiveState Board Member and Red Hat CTO Michael Tiemann